In plants for production of medicines and containers such as hygienic bottles for aseptic filling with beverages, food, and the like, the surface of production equipment that comes into direct or indirect contact with the containers or products, or the surface of the containers, or the inner surface of a space (called collectively hereinbelow as “the surface of a space-to-be-sterilized”) requires a high level of cleaning at all times. The techniques, whether conventional or novel, for sterilizing the surface of a space-to-be-sterilized are particularly indispensable in production of containers such as hygienic bottles for aseptic filling. A variety of methods have been suggested for such sterilization, but a definitive technique has not yet been developed, and the sterilization remains one of the important technological tasks that should be contested at the production site. The reason therefor is that the technique for sterilizing the surface of a space-to-be-sterilized appears, while appearing to be simple at a first glance, should take into account: (1) the selection of a suitable sterilizing agent corresponding to the type of bacteria to be sterilized, so that the desired bactericidal effect is obtained; (2) the effect on the health of workers and the environment; (3) the cost of sterilization equipment; (4) the cost of human labor; (5) the effect produced on efficiency of production line, such as sterilization time; and (6) the effect produced on the products, and all of the aforementioned conditions should be satisfied. However, the conventional techniques for sterilizing the surface of a space-to-be-sterilized have both merits and demerits, and the method satisfying all of the conditions has not yet been suggested.
Where the conventional techniques are examined from the standpoint of the aforementioned conditions (1) to (6), one of the methods for sterilizing the surface of a space-to-be-sterilized includes impregnating a cloth or the like with a sterilizing agent such as alcohol and wiping with the cloth. However, the problem associated with alcohol sterilizing agents is that although such agents are effective for general sterilization, they are not effective against spore-forming bacteria, and for some sterilization objects, a problem is associated with the aforementioned condition (1). Further, with such a method, a long time is required for wiping in the case of a wide space and the cost of human labor rises. Meanwhile, the surface of a very narrow space is difficult to wipe sufficiently and problems are also associated with the conditions (4) and (5).
Aqueous solutions of hydrogen peroxide or aqueous solutions of peracetic acid have been used as sterilizing agents against spore-forming bacteria. A 35% aqueous solution of hydrogen peroxide is typically used as hydrogen peroxide for surface sterilization, and the following sterilization methods have been suggested: a method by which a 35% aqueous solution of hydrogen peroxide and sterilized air are sprayed from a two-fluid nozzle inside an aseptic chamber, then heated sterilized air is fed in for 30 minutes, and the sterilizing agent is removed by evaporation (Patent Document 1), a method by which a 35% aqueous solution of hydrogen peroxide is gasified and condensed to obtain hydrogen peroxide mist which is forcibly introduced into a chamber and agitated (see Patent Documents 2 to 4), and a method by which a space to be treated is filled with gasified aqueous solution of hydrogen peroxide (Patent Documents 5 and 6).
However, since an aqueous solution of hydrogen peroxide with a high concentration of 35% is used, where such solution gets on the skin, a severe burn occurs. Hence, it is necessary to wear protective clothing, protective eyeglasses, and a mask and wait till the sprayed solution is dried. Therefore, in this case, problems are associated with the conditions (2) and (5). Furthermore, in order to ensure sufficient contact of the gasified sterilizing agent with the sterilization object surface and prevent the sterilizing agent from leaking to the outside, air-tight space equipment with high-level shielding of the space-to-be-sterilized is required. In addition, a waste gas treatment apparatus is required for detoxifying the waste gas, huge investment in equipment is required and problems are associated with the aforementioned condition (3). Accordingly, a variety of methods for sterilizing the surface of a space-to-be-sterilized have been suggested that involve such sterilization by gasification of a sprayed sterilizing agent as described above, but since a high-cost equipment is required for protection against the gasified high-concentration sterilizing agent, practically none of such methods has been put to practical use, and a method by which an aqueous solution of a sterilizing agent is directly injected or sprayed on the sterilization object and then washed with aseptic water has been generally used for sterilizing a space with chemical agents. However, such a method is not suitable for sterilization objects that are adversely affected by wet conditions. Other problems include low sterilization efficiency and the necessity to use large amounts of the sterilizing agent and washing water. Furthermore, when a sterilizing agent is simply applied and then naturally dried, a long time is required for complete removal thereof and problems are associated with the aforementioned conditions (5) and (6).